The present studies are directed toward localizing, by electron microscopic techniques, the major components of the streptococcal cell wall. In addition to localization of the major cell wall antigens, more precise ultrastructural definition of M-protein will be carried out so as to aid in studying attachment of M+ streptococci to human leukocytes, in vitro. Such streptococcal-leukocyte surface interactions will be studies by by critical point drying and transmission electron microscopy.